In a fuel injection valve of this type, a seal means for preventing fuel leakage must be provided at the joint between the connection member and the socket portion. It is customary practice to form a groove from an O-ring around the outer circumference of the socket portion, or to form an expanded portion around the outer circumference of the socket portion to ensure a wide seal area for the joint surface. However, such a groove or expanded portion is generally formed by cutting into the socket portion, and the swarf i.e. dust and particles from the cutting can adhere to the fuel passage, so that cleaning must be effected to remove the swarf. Particularly, in a fuel injection valve of this type, fuel is supplied under high pressure into the fuel passage, so that if swarf adheres to a portion close to the valve body (including the seat surface of the valve seat) and is deposited on the downstream side of the fuel passage, fuel leakage is likely to develop, as is well known in the art. For this reason, the cleaning must be accurate and thorough, but the workability of this cleaning is not sufficiently high.